The basic idea of positioning a roller type of window screen vertically in a window frame to change its effective area of screening is old in the art. Various devices have been patented and those known to the applicant at this time are summarized briefly below.
Thiel U.S. Pat. No. 394,737 takes an ordinary roll up type of window shade and instead of mounting it at the top of the window opening, provides for its riding on guide rods at the sides of the window with a pulley and rope arrangement to raise and lower the screen roller to any desired position.
Hewas, et al U.S. Pat. No. 707,413 accomplishes the same as Thiel without the use of side rails and employs double rope and pulley arrangements with cross ropes and frames holding the screen roller and permitting its raising and lowering by means of suitable rope and fastener arrangement.
Brown U.S. Pat. No. 938,207 teaches the use of angle iron brackets at the sides of the window providing rails from which "L" shaped plates are permitted to ride, said plates holding the roller in position, which may be altered by the use of suitable rope and pulley arrangement mounted on the window frame and attached to the slide plates holding the roller.
Britting U.S. Pat. No. 1,129,162 also employs side rails on the window with a horizontal guide and ball bearing pulleys for the guide to ride upon the location being maintained by suitable rope attachments to the guides.
South U.S. Pat. No. 1,250,043 utilizes a horizontal channel to hold the roller and a rope and pulley arrangement with fasteners to position the roller and hence the screen vertically with respect to the window opening.
Joseph U.S. Pat. No. 1,303,678 teaches the use of horizontal metal slats to hold the screen roller which are positioned vertically in the window screen by means of chain and sprocket combinations, provision being made to hold the chain in a given position and consequently provide for changing the location of the roller.
Reeder, U.S. Pat. No. 3,878,878 utilizes threaded rods and nuts positioned vertically on opposite sides of the window frame which may be rotated, thus causing the travel of the nuts which are made a part of the roller frame supports and thus provide for a change in vertical position on the screen.
Thus it is seen that all the prior art relies on combinations of pulleys, or chains, or screws with their attendant followers which attach to the rotating roller forming an upper part of the screen which is usually of a conventional type to locate this upper roller upon which the screen is rolled up in different positions to effect partial screening of the window in any portion desired. The rolling and unrolling of the screen is accomplished in a conventional manner in all of the prior art, that is by spring action of the roller.